Heat Generating Composition, Heat Generating Body, and Process for Producing Heat Generating Body

Abstract

There are provided a heat generating composition and a heat generating body having excellent exothermic rising properties and having exothermic holding properties over a long period of time and a process for producing the same. The invention is concerned with a heat generating composition, characterized in that the heat generating composition contains, as essential components, an iron powder, a carbon component, a reaction accelerator, a hydrogen formation inhibitor and water; that the iron powder contains from 20 to 100% by weight of an active iron powder; and that the active iron powder is at least any one of an active iron powder in which at least a part of the surface of an iron powder is covered by an iron oxide film and a thickness of the iron oxide film is 3 nm or more, and which has a region of an oxygen-free iron component in at least one region selected from a central region of the active iron powder and a region beneath the iron oxide film, and an active iron powder in which an amount of wustite is from 2 to 50% by weight in terms of an X-ray peak intensity ratio to iron.

1 . A heat generating composition, characterized in that the heat generating composition contains, as essential components, an iron powder, a carbon component, a reaction accelerator, a hydrogen formation inhibitor and water; that the iron powder contains from 20 to 100% by weight of an active iron powder; and that the active iron powder is at least any one of: 
 1) an active iron powder comprising particles, a surface of each of which is at least partially covered with an iron oxide film and a thickness of the iron oxide film is 3 nm or more, and which has a region of an oxygen-free iron component in at least one region selected from a central region of the particle and a region beneath the iron oxide film, and    2) an active iron powder in which an amount of wustite is from 2 to 50% by weight in terms of an X-ray peak intensity ratio to iron.    
   
   
       2 . The heat generating composition according to  claim 1 , characterized in that the amount of wustite of the active iron powder is from 5.01 to 50% by weight in terms of an X-ray peak intensity ratio to iron.  
   
   
       3 . The heat generating composition according to  claim 1 , characterized in that the heat generating composition contains at least one member selected from additional components consisting of a water retaining agent, a water absorptive polymer, a pH adjusting agent, an aggregate, a fibrous material, a functional substance, a surfactant, an organosilicon compound, a pyroelectric substance, a moisturizer, a fertilizer component, a hydrophobic polymer compound, a heat generating aid, a metal other than iron, a metal oxide other than iron oxide, an acidic substance, and a mixture thereof.  
   
   
       4 . The heat generating composition according to  claim 1 , characterized in that the heat generating composition has a water mobility value showing an amount of surplus water of less than 0.01.  
   
   
       5 . The heat generating composition according to  claim 1 , characterized in that the heat generating composition contains surplus water having a water mobility value of from 0.01 to 20 and has moldability by the surplus water; and that the surplus water in the heat generating composition does not reveal a function as a barrier layer, whereby an exothermic reaction with air is not inhibited.  
   
   
       6 . The heat generating composition according to  claim 1 , characterized in that the heat generating composition contains surplus water having a water mobility value of exceeding 20 and not more than 50 and has moldability by the surplus water; and that the surplus water in the heat generating composition reveals a function as a barrier layer, whereby an exothermic reaction with air is inhibited.  
   
   
       7 . A heat generating body, characterized in that the heat generating composition according to  claim 1  is accommodated in an air-permeable accommodating bag to form an exothermic part.  
   
   
       8 . The heat generating body according to  claim 7 , characterized in that the accommodated heat generating composition is a heat generating composition molded body.  
   
   
       9 . The heat generating body according to  claim 7 , characterized in that the accommodated heat generating composition forms sectional exothermic parts sectioned into plural sections by a seal part within the air-permeable accommodating bag; and that an exothermic part is formed from gathering of the sectional exothermic parts.  
   
   
       10 . The heat generating body according to  claim 9 , characterized in that the sectional exothermic parts have a longest width of from 1 to 55 mm and a maximum height of from 0.1 to 10 mm; that a space of the sectional exothermic parts is from 0.5 to 30 mm; that the surroundings of the heat generating composition molded body are heat sealed to form sectional exothermic parts; that at least a part of the accommodating bag has air permeability; and that the periphery which becomes the heat generating body is sealed.  
   
   
       11 . The heat generating body according to  claim 9 , characterized in that the heat generating composition molded body has a curved shape; and that the sectional exothermic parts have a curved shape and have a shortest radius of curvature of from 0.5 to 27.5 mm and a height of from 0.1 to 15 mm.  
   
   
       12 . The heat generating body according to  claim 7 , characterized in that a fixing measure is provided on the exposed surface of the heat generating body and optionally provided with a separator.  
   
   
       13 . A process for producing a heat generating body, characterized by accommodating a heat generating composition which contains, as essential components, an iron powder containing from 20 to 100% by weight of at least one of: 
 1) an active iron powder comprising particles, a surface of each of which is at least partially covered with an iron oxide film and a thickness of the iron oxide film is 3 nm or more, and which has a region of an oxygen-free iron component in at least one region selected from a central region of the particles and a region beneath the iron oxide film, and    2) an active iron powder in which an amount of wustite is from 2 to 50% by weight in terms of an X-ray peak intensity ratio to iron, a carbon component, a reaction accelerator, a hydrogen formation inhibitor and water in an air-permeable accommodating bag.    
   
   
       14 . The process for producing a heat generating body according to  claim 13 , characterized in that the heat generating composition contains at least one member selected from additional components consisting of a water retaining agent, a water absorptive polymer, a pH adjusting agent, a surfactant, an organosilicon compound, a hydrophobic polymer compound, a pyroelectric substance, an antioxidant, an aggregate, a fibrous material, a moisturizer, a functional substance, and a mixture thereof.  
   
   
       15 . The process for producing a heat generating body according to  claim 13 , characterized in that the heat generating composition as accommodated in the air-permeable accommodating bag forms sectional exothermic parts sectioned into plural sections by a seal part within the air-permeable accommodating bag.  
   
   
       16 . The process for producing a heat generating body according to  claim 13 , characterized in that the heat generating composition is a molded body, is provided in a packaging material made of a substrate and a covering material constituting the air-permeable accommodating bag and seals the surroundings of the heat generating composition molded body to produce a heat generating body.